In recent years, in association with size reduction and weight saving of electronic equipment, demands for a high energy density battery as a power supply are increasingly growing. A storage battery in which a metal such as lithium, zinc or the like is contained in the negative active material has an advantage that energy density per unit mass and power density are high. Such storage batteries are studied to be used practically as a power supply of electronic equipment and vehicles.
However, there is a problem that a dendrite may grow from the metal such as lithium and zinc contained in the negative active material to cause shortage due to penetration of a separator and the dendrite causes a charge-discharge cycle life to decrease. Thus, an additive is conventionally added to an electrolyte against such a problem.
JP-A-2013-84349 discloses “an electrolyte solution for an alkaline battery, wherein the electrolyte solution contains at least an organic substance having two or more carbon atoms and one or more hydroxyl groups in its molecule.” See claim 1.
It is an object of JP-A-2013-84349 “to provide an electrolyte solution for an alkaline battery and an alkaline battery which suppress generation of a hydrogen gas produced by a side reaction, a dendrite formed when zinc is precipitated, and a change in shape of zinc and can realize a prolonged charge-discharge cycle and an excellent charge-discharge efficiency.” See paragraph [0007].
Further, it is disclosed that “the number of hydroxyl groups is preferably 5 or less”, and a monohydric alcohol, a dihydric alcohol and a trihydric alcohol which have 2 to 6 carbon atoms are exemplified as the organic substance. See paragraphs [0017], [0019] and [0020].
JP-A-2009-93983 discloses “a secondary battery in which a negative electrode and a positive electrode are arranged with an electrolyte solution interposed therebetween, wherein the negative electrode includes, as a negative active material, a material which absorbs/releases metal ions, and the electrolyte solution includes at least one dendrite forming inhibitor selected from the group consisting of polyalkylene imines, polyallylamines and asymmetrical dialkyl sulfones.” See claim 1. Also, it is disclosed that “the negative electrode includes a material selected from the group consisting of zinc, magnesium, aluminum and an alloy thereof.” See claim 6.
It is a main object of JP-A-2009-93983 “to provide a secondary battery capable of performing charge-discharge repeatedly suppressing formation of a dendrite.” See paragraph [0005].
Further, it is disclosed that in a zinc-air battery including, as an electrolyte solution, a 6N hydroxy aqueous solution containing polyethyleneimine (PEI) added in an amount of 1 wt %, the formation of a dendrite is suppressed and charge-discharge could be performed repeatedly. See paragraph [0018].
JP-A-2003-297375 discloses “an alkaline zinc battery including a negative electrode containing zinc or a zinc alloy as a negative active material, a positive electrode, a separator, and an alkaline electrolyte solution, wherein the alkaline electrolyte solution is formed by including a cationic organic substance in a 10 wt % to 30 wt % potassium hydroxide aqueous solution.” See claim 1. Further, it is proposed that the cationic organic substance is “any one or more of a quaternary ammonium salt, a quaternary phosphonium salt, and a tertiary sulfonium salt,” and “the alkaline zinc battery . . . which is a secondary battery.” See claims 2 and 7.
It is an object of JP-A-2003-297375 “to realize an alkaline zinc secondary battery which prevents expansion and liquid leakage of a battery associated with generation of a hydrogen gas, and an internal short-circuit due to nonuniform growth of dendric or spongy zinc in a zinc negative electrode, and is excellent in liquid leakage and a cycle life.” See paragraph [0076].
Further, in Example of alkaline zinc secondary battery, “n-dodecyl trimethyl ammonium chloride” and a long chain alkyl trimethyl ammonium salt are disclosed for the cationic organic substance to be added to an electrolyte solution. See paragraphs [0171] to [0245]. Further, it is proposed that “it is preferred that a concentration of a potassium hydroxide aqueous solution is set to 30 wt % or less in order to surely dissolve the cationic organic substance in 0.1M or more and a saturated amount or less.” See paragraph [0216]. Also, it is disclosed that “it is found that liquid leakage and an internal short-circuit of the alkaline zinc secondary battery are significantly suppressed when the number of carbon atoms of the long chain alkyl group of the cationic organic substance is 3 or more,” and “however, when the substituent has 15 or more carbon atoms, particularly 21 or more carbon atoms, a discharge capacity is reduced, and therefore the number of carbon atoms of the long chain alkyl group of the cationic organic substance is 3 to 20, and particularly preferably 3 to 15.” See paragraph [0229].
JP-A-2014-199815 discloses “an electrode surface coating forming agent including a nitrile compound.” See paragraph [0001]. As a problem to be solved, it is shown that “an improvement of stability of an electrolyte solution at high-temperature is required in order to improve the safety of a lithium ion battery.” See paragraph [0003]. With respect to the nitrile compound, it is disclosed that “charge-discharge efficiency can be increased because a stable protective film is formed on the surface of the electrode by these compounds,” and “further, a dendrite phenomenon of lithium metal can be suppressed by the stable protective film.” See paragraph [0051]. Also, it is disclosed that “a compound having a nitrile group used for the electrode surface coating forming agent of the present invention may be used alone; however, it is contained in an organic solvent-based electrolyte solution commonly used in an amount of usually about 0.1 to 80 wt %, preferably about 1 to 50 wt %, and more preferably about 5 to 30 wt %.” See paragraph [0052].
In JP-A-2014-44908, with respect to “a metal air battery” in which an electrode active material is “metal zinc” (claims 1, and 11), it is disclosed that “the air electrode 6 may be disposed so as to be in contact with an ion-exchange membrane 8 which is in contact with an electrolyte solution 3 stored in an electrolyte solution tank 1,” and “the ion-exchange membrane 8 may be an anion exchange membrane.” Further, it is disclosed that “since the anion exchange membrane has a cation group serving as a fixed ion, the cation in the electrolyte solution cannot conduct to the air electrode 6. In contrast with this, since hydroxide ions produced at the air electrode 6 are anions, they can conduct to the electrolyte solution. From this, a battery reaction of a metal air battery 45 can proceed, and the cation in the electrolyte solution 3 can be prevented from moving to the air electrode 6. From this, precipitation of metal or a carbonate compound at the air electrode 6 can be suppressed.”
JP-A-8-130034 discloses “a Li secondary battery, wherein the battery has a positive electrode layer on a porous insulating film side and a negative electrode layer on a cation exchange membrane side of a separator composed of the electrolyte solution-retainable porous insulating film and the cation exchange membrane.” See claim 1. As a problem to be solved, it is shown that “a problem of a shortened battery life is significant as lithium or a lithium alloy, particularly a lithium alloy in which lithium is rich is used for the negative electrode for the purpose of improving an electromotive force or a charge-discharge capacity.” See paragraph [0003]. Further, it is disclosed that “addition of a cation exchange membrane to a negative electrode layer side of a conventional separator made of a porous insulating film prevents or inhibits lithium from becoming a compound on the surface of the negative electrode to be precipitated.” See paragraph [0008].
In JP-A-2005-123059, it is disclosed “an air zinc battery in which an air diffusing layer, a water-repellent film, a positive electrode catalyst layer, and a separator are layered in turn on a positive electrode case having air holes, and a gel-like zinc negative electrode housed in a negative electrode container is opposed to the positive electrode catalyst layer with the separator interposed therebetween, wherein the separator has a first layer made of a semipermeable membrane or a microporous membrane and a second layer made of a nonwoven fabric or a woven fabric, and the separator is arranged so that the second layer is positioned on the positive electrode catalyst layer side.” (See claim 1.) Also, it is proposed that “the nonwoven fabric or the woven fabric arranged on the positive electrode catalyst layer side of the separator is excellent in liquid retainability compared with the semipermeable membrane and the microporous membrane, and water and hydroxide ions move smoothly by reducing contact resistance between the separator and the catalyst layer,” and “particularly, it is possible to suppress an increase of internal resistance resulting from lack of an electrolyte solution in the separator on the catalyst layer side.” See paragraph [0014].
JP-A-60-136182 discloses “an air battery including a gel-like zinc cathode formed by mixing an amalgamated zinc powder, an alkaline electrolyte solution and a gelating agent.” Also, it is proposed that “the alkaline electrolyte solution includes sodium hydroxide or a potassium hydroxide aqueous solution, a concentration of the solution is 4 to 12 mold, a mixing ratio is set to a range of 0.3 to 3 wt %, the gelating agent includes a carboxyvinyl polymer having a molecular weight of 100000 to 5000000, and a mixing ratio of the gelating agent is 0.3 to 3 wt %.”